The invention relates to a loom shedding motion in which a number of cams are secured to a shaft and adapted to drive pivoted cam follower levers. Thrust rods are connected thereto and pivoted bent levers are connected to the thrust rods. The bent levers have a central bearing, one arm on their input side and one arm on the bearing of the bent lever. Motion-transmitting pivots are positioned at the ends of the arms
The normal practice in modern shedding motions is to provide two cams to drive a single cam follower lever, so that the shedding elements of the loom are positively driven in both directions of movement. The space required axially of the drive shaft to accommodate a pair of cams and a cam follower lever is greater than the space required at the output end pivots of the bent levers in the direction of the pivot axes. Relatively slender elements for transmitting the motion to the leaves of the loom are positioned in the pivots. The spacing between the leaves, i.e., the distance between the center plane of any leaf and the center plane of an adjoining leaf, is normally the same as the spacing between the pivots at the output ends of the bent levers. Since the spacing between the cam follower levers in the shedding motion is greater than the spacing between the bent levers at their output ends, the bent levers of prior art shedding motions are provided with crank or offset portions in one of their arms. The crank or offset portions extend between the bearing of the bent lever and the output end pivot. The degree of offset or crank is greater in proportion to the distance the bent lever is from the center of a group of adjacent levers of a shedding motion. An arrangement of this kind is known, for example, from German patent specification No. 2 441 353. In this known construction there is a considerable axial offset between the bearing and the output end pivot of the outer arms of a lever group. In comparison, the axial offset between the pivots where the thrust rods are connected and the bearings of the bent levers is negligibly small at the input end of the opposite arms of the bent levers. Because of the relatively substantial crank or offset of the lever arms which extend to the output end, the reaction forces produced by the transmission elements of the shedding motion producing high bending moments which may lead to excessive tilting of the bearings of the bent levers and therefore to overstressing of the spindle carrying such levers or in the bearings.
It is the object of the invention to provide a device producing a shedding motion obviating tilting excessive in the bearings of the bent levers.
According to the invention, the arms are so cranked or offset that, as seen in a view perpendicular to their bearing axis, the group of the bent levers has a fan shape in which the distance from one pivot to the other at the output end is less than the distance from one bearing center to the other and the distance from one bearing center to the other is less than the distance from one pivot to the other at the input end. In this arrangement, the angles between the connecting lines, from the centers of the pivots of any lever to the center of the same lever bearing may differ by at most 8.degree.. Ideally these connecting lines form a straight line. In every case, there are in each group of levers distances equal between adjacent pivots at the input of the bent levers, and equal spacings between their bearings and also equal spacings between adjacent output end pivots. The connecting lines form with the axis of the bent levers an angle of about 90.degree.. The angles decrease from the center of the whole group of levers towards the outside of the group of levers by a reduced amount of from 1.degree. to 5.degree..
The bent levers according to the invention in particular operate with very reduced wear and require little lubricant.